Uhh, im a bit terrible at explaining things, but i tried out what you wanted to do and ended up with this (couldn't stop the text from being effected :?)
Ill try to explain how i did it :P :
I took the image of the dj mike sig then pasted the background you want over it on a new layer, went into blending options and selected 'difference' as the blend mode, and then got rid of the bits that i didn't need :)
Hope that helps.. ^^